Fine granulator



March 22, 1966 w. M. SHELDON 3,241,776

FINE GRANULAIOR Filed April 29, 1963 5 Sheets-Sheet l INVENTOR. 4WILLIAM M. SHELDON wfwew ATTORNEY March 22, 1966 w. M. SHELDON 3,241,776

FINE GRANULATOR Filed April 29, 1963 5 Sheets-Sheet 2 INVENTOR WILLIAMM. SHELDON ATTORNEY March 22, 1966 w. M. SHELDON 3,241,776

FINE GRANULA'IOR Filed April 29, 1965 5 Sheets-Sheet 3 INVENTOR.

WILLIAM M. SHELDON March 22, 1966 w. M. SHELDON FINE GRANULATOR 5Sheets-Sheet 4 Filed April 29, 1963 ATTORNEY March 22, 1966 w. M.SHELDON FINE GRANULATOR 5 Sheets-Sheet 5 Filed April 29, 1963 INVENTOR.WILLIAM M. SHELDON ATTORNEY United States Patent 3,241,776 FKNEGRANULATOR William M. Sheldon, Elizabeth, N.J., assiguor to PulverizingMachinery Division of Slick Industrial Company, Washington, D.C., acorporation of Delaware Filed Apr. 29, 1963, Ser. No. 276,645 6 Claims.(Cl. 241-55) This invention relates to the comminution of material andparticularly to an improved apparatus for effecting comminution ofsuspended material by cutting impact on a shearing edge in the presenceof a selectively directed gaseous carrier.

Comminution of material by impact pulvenization is Widely employed inthe commercial arts and widely varying types of apparatus are utilizedin accord with the type of material to be comminuted and the desiredparticle size range of the resulting comminuted .product. Cornminutingapparatus of the so called hammer mill types are Widely used foreffecting impact pulverization of materials to a particle size range ofabout 5000 to 40 microns. Such hammer type mills are generallycharacterized by a high speed rotating shaft having mounted thereon a.plurality of hammerlike members. Most, if not all, mills of this typeeffect reduction by impact, while the material is in suspension, inconjunction with an associated breaker surface usually constituted by apart of the housing surrounding the rotating elements. Such mills,however, are usually characterizedby the production of what for many enduses is an unacceptable amount of ultra fines and an undue amount ofheat generation. The development of such ultna fines is usuallyobjectionable as, for example, when the comminuted material is to beused in forming tablets or for injection molding. The development ofundue amounts of heat is particularly objectionable in the handling ofmaterials that tend to agglomerate, either by release of Water ofcombination or hygroscopicity or by reason of sensitivity totemperature.

This latter problem has become of increasing importance with continuallyexpanding use of synthetic resins and so called plastics and otherpolymerization products, many of which are somewhat resilient in natureand/or have a tendency to become soft and plastic beyond certaintemperatures. In the attempted handling of materials of the types abovenoted in conventional hammer mill type apparatus various expedients,such as the prereduction of product temperature or of ambient airtemperature by the utilization of Dry Ice or other refrigerants havebeen employed to limit the degree of temperature rise and to limit themaximum temperatures attained during comminution. Such expedients,however, are palliative in nature at best and, apart from the additionalexpense involved, have been characterized with a marked lack ofcommercial utility due to necessarily reduced production, increased costand in some instances, the necessity of removing, by a subsequent dryingoperation, atmospheric moisture condensation that becomes incorporatedin the comminuted material.

This invention may be briefly described as an improved apparatus foreffecting comminution of suspended material by cutting impact withrapidly moving acute angle shearing edges in a rotor induced selectivelydirected gaseous carrier which conveys heat or other agglomerationinducing factors away from the locus of material deformation and servesto rapidly reduce the temperature of the comminuted product.

Among the advantages of the subject invention is the permittedcomminution, at ambient air temperatures and with a markedly decreasedtemperature rise, of an extended range of materials including many, ifnot most,

Patented Mar. 22, 1966 of those whose comminution is effected only withdifficulty, if at all, in convention-ally constructed impactpulverization apparatus even with the expedients above noted. Otheradvantages of the subject invention include a marked increase in inducedflow of gaseous carrier into and through the locus of deformation, animproved control of particle size range of the resulting product and theavoidance of the production of undue amounts of ultra-finescharacteristic of impact pulverizat-ion operations. Still otheradvantages include the provision of greatly extended effective lengthsof cutting edge markedly improved yields per unit power input and asimplicity of construction that permits appreciable economies both ininitial cos-t and maintenance of apparatus embodying the subjectinvention,

The primary object of this invention is the provision of an improvedapparatus for effecting comminution of suspended material by cuttingimpact with a rapidly moving shearing edge in a rotor inducedselectively directed gaseous carrier which serves to convey heat orother agglomeration inducing factors away from the locus of materialdeformation and rapidly reduces the temperature of the comminutedmaterial.

Another object of this invention is the provision of improved apparatusfor effecting comminution of agglomerative materials.

Other objects and advantages of the invention will be set forth in thefollowing specification and claims and will be ascertainable from theappended drawings which illustrate, by way of example, the principles ofthe invention as the same are incorporated in a presently preferredembodiment of a oomminuting apparatus.

Referring to the drawings:

FIGURE 1A is an oblique view, partially broken away, of a mill (wth thehousing cover removed) incorporating the principles of this invention;

FIGURES 1B and C are side elevational and plan views, respectively, ofthe mill illustrated in FIGURE 1A and with the housing cover in place;

FIGURE 2 is a schematic and somewhat idealized plan view of theessentials of the comminution chamber and rotor assembly containedtherein as the same would be viewed with the housing cover portionthereof removed;

FIGURE 3 is a sectional view taken on the line 3-3 of FIGURE 2;

FIGURE 4 is a side elevation, in enlarged scale, of a presentlypreferred configuration for a fan blade type spacer element;

FIGURE 5A is a schematic representation of an air injector type ofmaterial feed which may be utilized in conjunction with the subjectmill;

FIGURE 5B is an enlarged oblique view of a preferred configuration forthe saw teeth on the rotor assembly.

Referring to the drawings, there is provided a housing assembly,generally designated 1 and formed of a base member 4 and a substantiallysemi-cylindrically shaped upper or cover member 6 removably securablethereto. The base and cover members 4 and 6 are shaped to generallydefine an internally disposed comminution chamber 3, a material feedchannel 5 communicating therewith and a dependent receiving chamber 7for the comminuted material after the same passes through thesemicylindrically shaped screen member 32 which also serves tocooperatively define the above mentioned comminution chamber 3. As bestillustrated in FIGURE 1B, the cover member 4 is provided with aplurality of particularly located circular air inlet apertures 16,suitably three, in each of the side Wall portions 26, 28 thereof, aswell as a material entry aperture 8 in alignment with the feed channel 5to accommodate material entry into the comminution chamber 3 by a wormtype feed mechanism generally designated 10. The air inlet apertures 16are preferably screened with a coarse screen or mesh of suitable size asto prevent egress of uncomminuted material therethrough but yet notimpede air flow therethrough into the comminution chamber.

The base housing member 4 is suitably shaped to terminally support theextending arms 12 of a pair of suspended rotor supporting journals orbearing assemblies 14. A rotor shaft 22 is rotationally supported in thejournals 14 and is provided with an extension end 24 extending beyondone side of the housing for facilitating a drive connection thereto. Asbest shown in FIGURES 2 and 3, the internally disposed comminutionchamber 3 is essentially of cylindrical configuration being defined bythe apertured and essentially planar wall portions 26, 28, an uppercurved wall 30 of essentially semi-cylindrical configuration and a lowercurved wall formed by the perforate and removable plate or screen 32 ofcomplemental semi-cylindrical configuration. As will be apparent tothose skilled in this art, the removable lower screen 32 is providedwith apertures of predetermined size to determine the maximum particlesize of the comminuted material that is permitted to exit from thecomminution chamber.

Disposed within the comminuation chamber 3 is a rotor assembly formed ofa plurality of circular saw-like blades or serrated periphery disc-likemembers 34 fixedly mounted on said rotor shaft 22 and maintained inclose parallel spaced relation by interposed spacer washers 36. Asillustrated in FIGURES 1A, 2 and 3, the disc-like members 34 areperipherally saw toothed so as to present a succession of cutting edgesin the direction of rotation and, for most applications are preferablycollectively mounted in a slightly skewed or offset relation asindicated by the angle A (FIGURE 2) to a plane normal to the axis ofrotation of the shaft 22 to minimize, if not prevent, undesired trackingof material introduced through the feed channel 5. As best illustratedin FIGURE B the saw teeth on the periphery of the blade members 34 arepreferably shaped to provide a chisel-like, acute angle cutting edge 35disposed substantially parallel to the axis of the rotor shaft 22. Asillustrated, the trailing edge of each tooth declines so as tocompletely expose the cutting edge on the succeeding tooth. Theprovision of the above-described chisel-like cutting edge disposedsubstantially parallel to the rotor shaft axis results, when the numberof available teeth per blade and number of blades are considered, in agreatly increased effective length of cutting edge all localized withinand operatively displaceable through the locus of material deformation.Secured to the undersurface of the upper curved wall 30 and disposedremote from the material feed aperture 8 is a deflector type linermember 31 having a surface configuration disposed in facing relationwith the rotor periphery and of suitable contour to deflect material ina more or less radial direction back into contact with the cutting edgedperiphery of the saw toothed rotor.

As will be apparent from the foregoing, the saw tooth configuration ofthe periphery of the disc or blade members provides a plurality ofsuccessive selectively positively cutting edges, which, upon engagementwith the material, effect comminution primarily by a cutting impact witha rapidly moving chisel-shaped shearing edge, as distinguished from theso-called pure impact principle of grinding or comminution.

Referring again to FIGURES 2 and 3, each of the saw blade members 34 isprovided with a plurality of apertures 38, suitably four in number,preferably arranged in equiangular relation and disposed substantiallytangent to the periphery of the interposed spacer element 36 and insubstantial radial alignment with the screened air inlet apertures 16disposed in the opposite side wall portions of the cover member 6.Although discrete circular air inlet apertures 16 are preferred, asingle elongate arcuate aperture in each side wall subtending an arc ofabout degrees would also be suitable. As illustrated, the blade members34 are mounted on the rotor shaft 22 in such manner as to preferablydispose the blade apertures 38 in substantially axial longitudinalalignment. In the specifically illustrated embodiment wherein ambientair inlet apertures 16 to the comminution chamber are disposed on bothside Walls of the cover member 6, a balanced bidirectional air flowtoward the center of the rotor is obtainable by preferential utilizationof an unapertured or imperforate central blade member 34a and bybeveling or tapering the apertures in the blades on either side thereofso as to be divergent in the direction of the desired air flow, as bestshown in FIGURE 2. The inclusion of the beveled or tapered apertures 38in the saw blade members 34 and the alignment thereof in the mannerdescribed thus provides a plurality of channels for selectively directedgas flow, specifically a flow of ambient air, longitudinally of therotor 22. In addition thereto, the interposition of the spacer members36 intermediate adjacent blade members serves to separate the same andthereby define a plurality of radially disposed channels for selectivelydirected gas flow, each having a plurality of common junctions with theaforedescribed longitudinal channels.

It is to be understood that while the presently preferred embodiment isconstructed as above set forth, a balanced bidirectional gas flow willalso be obtained by utilization of an apertured but preferably unbeveledcentral blade 34a. Also, as now will be apparent to those skilled inthis art, other arrangements as to degree or selective direction ofbevel, and size and location of the saw blade apertures may be made asdesired to obtain optimum results with a particular machine and/ orparticular material to be comminuted, for example, un beveled apertures38 in association with interposed spacer washers 36 of the fan bladetype configuration, as illustrated in FIGURE 4, will also result in thedesired and selectively axially directed flow of the gaseous carrier. Inaddition thereto, other expedients, such as an injector type materialfeed, as illustrated in FIGURE 5A may be employed.

In operation of the subject unit, unidirectional high speed rotation ofthe rotor assembly effects a positively induced and greatly increasedprimary bi-directional flow of ambient air or other gaseous carrier intothe commiution chamber through the ambient air inlet apertures 16 oneach side of the housing, longitudinally of the rotor shaft 22 throughthe tapered or beveled apertures 38 therein and, intermediate each pairof blades 34, a secondary flow radially outward into and through thelocus of comminution, such radial flow being accelerated and reinforcedby the action of the fan type spacer members 36 when the same areemployed as heretofore described.

Although the mechanics of the above described rotor induced air flowpattern are not fully understood at the present time, it is believedthat it serves, in addition to maintaining the material to be comminutedin suspended and separated condition in the vicinity of thechisel-shaped blade cutting edges, to uniformly convey heat away fromthe locus of deformation and to markedly and rapidly reduce thetemperature of the comminuted product prior to the necessaryintersurface contact thereof required for agglomeration.

The effect of maintaining the material to be comminuted in suspended andseparated condition and uniformly conveying heat away from the locus ofdeformation has resulted, as shown in tests, with a saw tooth rotorembodying this invention, in the (1) production of granular grinds witha minimum of ultra-fines, (2) marked increased in the production rateper H.P./hr., (3) comminution, at satisfactory commercial rates, of manymaterials heretofore reduceable only at reduced rates and/or with theexpedients referred to earlier in conventional equipment, (4) reductionin grind temperatures, (5) avoidance of the need, in many cases, of theexpedients referred to earlier.

By way of example, in a recent comparative test on polystyrene havingDry Ice necessarily mixed herewith, a conventional machine incorporatinga standard stirrup type rotor produced 33 lbs. per hour of comminutedproduct at 3 /2 H.P. A saw tooth rotor unit embodying the principles ofthe subject invention operating on the same material produced anequivalent comminuted product at a rate of 60 lbs. per hour at 1. H.P.Other operative tests on varying materials have shown as much as a 4 to1 capacity ratio in favor of the subject invention over conventional andcommercially available equipment.

In another comparative test on cellulose propionate (a fibrous materialsimilar to cellulose acetate), a conventional machine with a bar hammerrotor produced 12.5 lbs. per H.P. hour of 92.6% through 40 mesh productwith a .039 Rd.Pt. screen. The production obtained by the unit embodyingthe subject invention and with an equivalent speed and screen, was 20lbs. per H.P. hour and of an average analysis of 94% through a 40 meshand with a grind temperature about 25 F. lower than that produced in theconventional machine.

In still another comparative test, pure gum nitrol rubber (Hycar) couldnot be satisfactorily comminuted in a conventional bar hammer rotormachine due to a rapid rise in temperature, softening of the material inthe grinding chamber and smoking of the material. The same material wasprocessed satisfactorily in a unit embodying the subject invention withA and A Rd.Pt. screens at respective capacities of 18.5 and 27 lbs. perH.P. hour.

In other tests on a polyester resin having a melting point of 235 F. anda softening point of between 110 F. and 115 F. an unsuccessful attemptwas made to produce a screened product of 100%, +40 mesh and maximum,--140 mesh using liquid CO as a coolant, on a bar type conventionalmachine. Using applicants device on the same material and withoutcoolant there was obtained a screen product analysing 100%, 40 mesh and140 mesh when grinding the resin with an anti-caking agent and 100%, 40mesh and 11.1% 140 mesh when no anti-caking agent was added. Thetemperature of the ground material never exceeded 98 F.

6 with a F. feed material and R. atmospheric temperature.

In general, and apart from the specific advantages delineated above,tests to date indicate that units incorporating the subject inventionproduce satisfactory results in about 80% of those cases wherein it hasbeen tested on materials which could not be satisfactorily processed byconventional equipment. Also, tests have shown that it is generallypossible to operate the subject unit at appreciably higher milltemperatures than can be tolerated with conventional pulverizingmachines. For example, it has been found possible with applicants deviceto process low density polyethylene at outlet temperatures as high as200 F. without any fusing in the comminution chamber. Nitrol rubber hasbeen suc cessfully run without fusing at outlet temperatures of 160 F.This feature is of extreme importance in increasing capacity andreducing the size of required equipment to do a particular job. It isalso indicative of the fact that something more than a simple reductionof heat rise is responsible for the unexpected beneficial and newresults that have been obtained from the subject construction to date.

In addition to the above mentioned comparative test results, the subjectinvention has been found to be particularly advantageous in theproduction of high density powdered sugar (47 /2 lbs. per cubic footpacked density) and which after comminution has been remarkably freefrom lumping, even though no starch was added before grinding. Testshave been run on lots of sugars from different refineries, andcomminution has been performed under a wide range of relative humiditieswith no apparent difference in the non-lumping storage characteristics.

Applicant is unable to explain this highly advantageous result except tosuggest that it may be due tothe combined features of maintaining thematerial to be comminuted in suspended condition and uniformly passingair through the suspended material while it is being comminuted,combined possibly with the additional fact that the material is beingcomminuted by a fast acting shearing action, on an acute angle cuttingedge.

The following is a list of random test results on various materialswhich to date have been found to be particularly adapted to comminutionby apparatus incorporating the subject invention:

Material Character Mill Lbs. per Grind temp.,F. HP-hr.

Cellulose propionate Fibrous and mod- 148 19. 0 49%, -40.

erately tough. Coconut, stripped Britt1e Egg Coilee, roasted beans d0 16 I Licorice extract Very brittle 1. 300 'i b PVC, chlorinated type #1Tough 140 7. 5 Polyester, pigmented resin--. do 146 3.3 Ptgyethyleile,and d0 7. 5 91%, -16.

ar ion ac Polyethylene and pigment Fine, granular 84 200 Excellent colorwitht2%% pigdispersion. men Polyethylene, L.D. reactor Tough 200 8 51%,-40.

flake.

Polystyrene 90 {1.3% +12.

16.6 -40. Polystyrene, pigmented, 5. 5 {47%,3-40. 50:50 T10 80.Potatoes, dried sliced, raw 200 {1%7, +10.

20 40. Resin, misc., A.C.X Moderately touglL 120 22.0 +40.

, -140. Rice Hard 210 +10.

49 (1, 10+50. -50+200. Rt i bberfiqitrol (crude) Tough, resilient." 4{Dig/b, +10

ype 36 R%bber,fiNitrol (crude) do 100 18 {4.0%, +20

ype '2. 51 5 Rubber, silicone flashiugs Tough 1.5 {4.5%, +20.

(cured). 82%, 20+50.

Material Character Mill Lbs. per Grind temp.,F. HP-hr.

Sugar Brittlc 104 190 {99.8%, 70.

88.3%, 200. Teflon and Fibre Glass, So1lt, fibrous 60 70:30 mix. umps.Vinyl scrap Tough 104 12 g fla r 0y -8- Wlir at Hard 4.10 13% Othermaterials which have also been found to be particularly suited forcomminution by apparatus incorporating the subject invention include:

Elastomers Leather scraps Nylon pellets Polyurethane Scrap rubberSynthetic crude rubber Vinyl resins.

Having thus described my invention, I claim:

1. A comminuting apparatus comprising housing means shaped to define asubstantially cylindrically shaped comminution chamber having a materialentry aperture, comminuted material egress means and a generally axiallydisposed gaseous carrier entry aperture therein,

a rotor assembly disposed within said chamber including an axiallydisposed rotatable shaft having a plurality of peripherally serrateddisc like blade members with acute angle cutting edges mounted in spacedrelation thereon and said blade members having apertures thereindisposed remote from the serrated peripheries thereof for providing,upon rotation of said rotor assembly,

a selectively directed primary flow of a gaseous carrier from saidgaseous carrier entry aperture longitudinally of said shaft intermediatesaid shaft and the periphery of said blade members and divertedsecondary flows of said gaseous carrier radially outward intermediatesaid disc like :blade members int-o and through a locus of deformationfor said material to be comminuted as defined by the path of travel ofthe serrated peripheries of said blade members.

2. The comminuting apparatus as set forth in claim 1 wherein said acuteangle cutting edges of said peripherally serrated disc like blademembers are disposed substantially parallel to the axis of said rotorassembly shaft and are advanceable in the direction of rotation thereof.

3. The comminuting apparatus as set forth in claim 1 including spacermeans disposed intermediate said disc like blade members to assist inthe radially outward displacement of said secondary flows of gaseouscarrier.

4. The comminuting apparatus as set forth in claim 1 wherein said disclike blade members are mounted in skewed relation upon said shaft.

5. A comminuting apparatus comprising housing means shaped to define asubstantially cylindrically shaped comminution chamber having agenerally axially disposed gaseous carrier entry aperture therein,

a rotor assembly disposed within said chamber including an axiallydisposed rotatable shaft having a plurality of peripherally serrateddisc like blade members with acute angle cutting edges mounted in spacedrelation thereon,

said blade members having apertures therein disposed intermediate saidshaft and the peripheries thereof for producing, upon rotation of saidrotor assembly,

a selectively directed primary flow of gaseous carrier through saidgaseous carrier entry aperture and longitudinally of said shaftintermediate said shaft and the periphery of said blade members anddiverted secondary fiows of said gaseous carrier radially outwardintermediate said disc like blade members to cooperatively confine,

with said housing means, suspended material to be comminuted within acomminuting zone of generally hollow cylindrical configuration whichenvelopes the locus of displacement of the serrated peripheries of saiddisc like blade members.

6. The comminuting apparatus as set forth in claim 5 wherein said acuteangle cutting edges of said peripherally serrated disc like blademembers are disposed substantially parallel to the axis of said rotorassembly shaft and are advanceable in the direction of rotation thereof.

References Cited by the Examiner UNITED STATES PATENTS 1,764,020 6/1930Hopkins 241-242 X 2,165,946 7/1939 Smith 24ll8 2,226,741 12/1940Randolph 241-51 X 2,293,728 8/ 1942 Freund 241-17 2,468,337 4/1949Lykken et a1. 241-55 2,601,953 7/1952 Savage 241-18 2,726,045 12/ 1955Hinerfeld 241l6 2,981,487 4/1961 Davis 241-242 X ROBERT C. RIORDON,Primary Examiner.

WILLIAM W. DYER, 111., I. SPENCER OVERHOLSER,

Examiners.

1. A COMMUNICATING APPARATUS COMPRISING HOUSING MEANS SHAPED TO DEFINE ASUBSTANTIALLY CYLINDRICALLY SHAPED COMMINUTION CHAMBER HAVING A MATERIALENTRY APERTURE, COMMINUTED MATERIAL EGRESS MEANS AND A GENERALLY AXIALLYDISPOSED GASEOUS CARRIER ENTRY APERTURE THEREIN, A ROTOR ASSEMBLYDISPOSED WITHIN SAID CHAMBER INCLUDING AN AXIALLY DISPOSED ROTATABLESHAFT HAVING A PLURALITY OF PERIPHERALLY SERRATED DISC LIKE BLADEMEMBERS WITH ACUTE ANGLE CUTTING EDGES MOUNTED IN SPACED RELATIONTHEREON AND SAID BLADE MEMBERS HAVING APERTURES THEREIN DISPOSED REMOTEFOR THE SERRATED PERIPHERIES THEREOF OF PROVIDING, UPON ROTATION OF SAIDROTOR ASSEMBLY, A SELECTIVELY DIRECTED PRIMARY FLOW OF A GASEOUS CARRIERFROM SAID GASEOUS CARRIER ENTRY APERTURE LONGITUDINALLY OF SAID SHAFTINTERMEDIATE SAID SHAFT AND THE PERIPHERY OF SAID BLADE MEMBERS ANDDIVERTED SECONDARY FLOWS OF SAID GASEOUS CARRIER RADIALLY OUTWARDINTERMEDIATE SAID DISC LIKE BLADE MEMBERS INTO AND THROUGH A LOCUS OFDEFORMATION FOR SAID MATERIAL TO BE COMMINUTED AS DEFINED BY THE PATH OFTRAVEL OF THE SERRATED PERIPHERIES OF SAID BLADE MEMBERS.